The compound 8-fluoro-2-{4-[(methylamino)methyl]phenyl}-1,3,4,5-tetrahydro-6H-azepino[5,4,3-cd]indol-6-one represented by formula 1
is a small molecule inhibitor of poly(ADP-ribose) polymerase (PARP). The compound of formula 1 and salts thereof, can be prepared as described in U.S. Pat. No. 6,495,541; PCT Application No. PCT/IB2004/000915, International Publication No. WO 2004/087713; and U.S. Provisional Patent Application Ser. No. 60/612,457, the disclosures of which are incorporated herein by reference in their entireties.
To date, eighteen enzymes have been identified by DNA sequence homology in the PARP family and the biochemical and enzymatic properties of seven have been investigated: PARP-1, and PARP-2 are stimulated by DNA strand breaks, PARP-3 interacts with PARP-1 and the centrosome, PARP-4 also known as vault PARP (VPARP), is the largest PARP and is associated with cytoplasmic vaults, tankyrase 1 and 2 (PARP-5a and 5b) are associated with telomeric proteins and the function of PARP-7 (TiPARP) is not clear at present but it may be involved in T-cell function and it can poly(ADP-ribosylate) histones (Ame J C, Splenlehauer C and de Murcia G. The PARP Superfamily. Bioessays 26 882-893 (2004)). Pharmacology studies have shown that the compound of formula 1 is an inhibitor of PARP-1 (Ki=1.4 nM) and PARP-2 (Ki=0.17 nM). Based on structural similarities in the amino acid sequences among the PARP enzymes, the compound of formula 1 likely binds with high affinity to the other members of the family as well.
Enzyme-mediated repair of single- or double-strand breaks in DNA is a potential mechanism of resistance to radiotherapy or cytotoxic drugs whose mechanism depends on DNA damage. Inhibition of DNA repair enzymes is thus a strategy for the potentiation of these agents. PARP-1, the best-characterized member of the PARP family, is a nuclear enzyme that upon activation by DNA damage mediates the transfer of ADP-ribose fragments from NAD+ to a number of acceptor proteins. Depending on the extent of DNA damage incurred, PARP-1 activation and subsequent poly(ADP-ribosyl)ation mediate the repair of the damaged DNA or induce cell death. When DNA damage is moderate, PARP-1 plays a significant role in the DNA repair process. Conversely, in the event of massive DNA damage, excessive activation of PARP-1 depletes ATP pools (in an effort to replenish NAD+), which ultimately leads to cell mortality by necrosis (Tentori L, Portarena I, Graziani G. Potential applications of poly(ADP-ribose) polymerase (PARP) inhibitors. Pharmacol Res 2002, 45, 73-85). This activation of PARP can also lead to release of AIF (apoptosis-inducing factor) triggering a caspase-independent apoptotic pathway. (Hong S J, Dawson T M and Dawson V L. Nuclear and mitochondrial conversations in cell death: PARP-1 and AIF. Trends in Pharmacological Sciences 25 259-264 (2004)).
As the result of the dual role of PARP-1, inhibitors of this enzyme, such as 8-fluoro-2-{4-[(methylamino)methyl]phenyl}-1,3,4,5-tetrahydro-6H-azepino[5,4,3-cd]indol-6-one represented by formula 1, may have a role as chemosensitizing agents (by preventing DNA repair, for example, after anticancer therapy), or as treatments for a variety of disease and toxic states that involve oxidative or nitric oxide induced stress and subsequent PARP hyperactivation. Such conditions include neurologic and neurodegenerative disorders (e.g., Parkinson's disease, Alzheimer's disease) (Love S, Barber R, Wilcock G K. Increased poly(ADP-ribosyl)ation of nuclear proteins in Alzheimer's disease. Brain 1999;122:247-53; Mandir A S, Przedborski S, Jackson-Lewis V, et al. Poly(ADP-ribose) polymerase activation mediates 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced parkinsonism. Proc Natl Acad Sci USA 1999;96:5774-9); cardiovascular disorders (e.g., myocardial infarction, ischemia-reperfusion injury) (Pieper A A, Walles T, Wei G, et al. Myocardial postischemic injury is reduced by poly(ADP-ribose) polymerase-1 gene disruption. J Mol Med 2000;6:271-82; Szabó G, Bährle S, Stumpf N, et al. Poly(ADP-ribose) polymerase inhibition reduces reperfusion injury after heart transplantation. Circ Res 2002;90:100-6; U.S. Pat. No. 6,423,705); inflammatory diseases, (Szabó C, Dawson V. Role of poly(ADP-ribose) synthetase in inflammation and ischaemia-reperfusion. TIPS 1998;19:287-98); diabetic vascular dysfunction (Soriano F G, Virág L, Szabó C. Diabetic endothelial dysfunction: role of reactive oxygen and nitrogen species production and poly(ADP-ribose) polymerase activation. J Mol Med 2001;79:437-48); arthritis (Szabó C, Virág L, Cuzzocrea S, et al. Protection against peroxynitrite-induced fibroblast injury and arthritis development by inhibition of poly(ADP-ribose) synthase. Proc Natl Acad Sci USA 1998;95:3867-72); and cisplatin-induced nephrotoxicity (Racz I, Tory K, Gallyas F, et al. BGP-15—a novel poly(ADP-ribose) polymerase inhibitor—protects against nephrotoxicity of cisplatin without compromising its antitumor activity. Biochem Pharmacol 2002;63:1099-111). Furthermore, it was shown that BRCA2 deficient tumor cells are acutely sensitive to PARP-1 inhibitors alone (Bryant H E, Schultz N, Thomas H D, Parker K M, Flower D, Lopez E, Kyle S, Meuth M, Curtin N J and Helleday T. “Specific killing of BRCA2 deficient tumors with inhibitors of poly(ADP-ribose)polymerase,” Nature: in press). PARP inhibitors are also involved in enhancing the induction of the expression of Reg gene in β cells and HGF gene and, accordingly, promote the proliferation of pancreatic β-cells of Langerhans' islets and suppress apoptosis of the cells (U.S. Patent Application Publication 2004/0091453; PCT Publication No. WO 02/00665). In addition, PARP inhibitors are also used in cosmetic preparations, especially in after-sun lotions (PCT Publication No. WO 01/82877). There are no marketed PARP inhibitors presently.
Cancer remains a disease with high unmet medical need. Cytotoxic chemotherapy remains the mainstay of systemic therapy for the majority of cancers, particularly late-stage disease. However, for patients with advanced or metastatic disease, few of the cytotoxic chemotherapy agents or regimens have been effective in increasing overall survival. Furthermore, the small therapeutic window associated with cytotoxic agents results in significant toxicity in conjunction with suboptimal efficacy. Therefore, a chemosensitizer that enhances the efficacy of cytotoxic drugs at well-tolerated doses would fulfill a critical need for cancer patients. U.S. Provisional Patent Applications No. 60/612,458 and 60/683,006, entitled “Therapeutic Combinations Comprising Poly(ADP-Ribose) Polymerases Inhibitor,” the disclosures of which are incorporated herein by reference in its entirety, describe pharmaceutical combinations of 8-fluoro-2-{4-[(methylamino)methyl]phenyl}-1,3,4,5-tetrahydro-6H-azepino[5,4,3-cd]indol-6-one.
To prepare pharmaceutical compositions containing 8-fluoro-2-{4-[(methylamino)methyl]phenyl}-1,3,4,5-tetrahydro-6H-azepino[5,4,3-cd]indol-6-one for administration to mammals, there is a need to produce this compound in a form having physical properties amenable to reliable formulation. Accordingly, there is a need in the art to provide improved forms of 8-fluoro-2-{4-[(methylamino)methyl]phenyl}-1,3,4,5-tetrahydro-6H-azepino[5,4,3-cd]indol-6-one having enhanced properties, such as improved solubility or bioavailability and stability to heat, moisture, and light.